Atom Substitution Defects of Hexagonal Boron Phosphide Suppress Charge Recombination

Abstract

Point defects, during e–h recombination, are a key factor in impacting optoelectronic device performance. Using nonadiabatic molecular dynamics (NAMD), here we investigate the nonradiative recombination of pristine, missing atom defects, including phosphorus vacancies (VP) and phosphorus and boron vacancies (VBP), and atom substitution defects, containing boron on the phosphorus site (BP) and phosphorus on the boron site (PB) of 2D monolayer hexagonal boron phosphide (h-BP). Carrier dynamics in the pristine h-BP and the defect engineered systems reveal that atom substitution defects BP and PB can suppress e–h nonradiative recombination. This is caused by the introduction of several low-frequency phonons in defect states. Electron–phonon coupling between the electronic state and these low-frequency phonons shortens the decoherence time and the nonadiabatic coupling. Also, the atom substitution systems with one defect state introduce fewer carrier recombination channels. Such a mechanism can be extended to other 2D materials with the same structure as h-BP.